Nowadays, great attention is paid to the study of circulating tumor cells (CTCs) due to their key role in distant metastasis. At the same time there is little data on the properties of circulating cells showing simultaneous expression of the leukocyte and epithelial markers and their possible role in tumor progression and chemotherapy resistance. The study was aimed to assess subpopulations of cells with hybrid epithelial/leukocyte phenotype and estimate the features of stemness, epithelial–mesenchymal transition (EMT), and integrin interface, which determine the cells’ possible metastatic properties in breast cancer (BC). The survey data from 128 patients with invasive breast carcinoma of no special type were included. Multicolor flow cytometry was used to assess the population structure and metastatic potential of the cells circulating in blood and primary tumor cells with hybrid phenotype. The primary tumor cell suspension was prepared by mechanical disaggregation. The high degree of heterogeneity was noted in the population of cells with hybrid phenotype, including the combination of the stemness and EMT features, and diverse integrin interface. Cells with hybrid phenotype are involved in the mechanisms underlying lymph node and distant metastasis. In lymph node metastasis, metastatic potential of these cells is associated with the stemness features (р = 0.0422) and co-expression of β3-, β4-, and αVβ5-integrins (р = 0.0338). In distant metastasis, metastatic potential of hybrid cells is associated with the stemness features (р = 0.015) and is not associated with the EMT features and integrin expression.